Yet another game I wish I'd waited to buy. It's not one I personally play much but I though it good enough to buy after getting back into real time strategy games a couple of years ago.. For around $8 (just under five pounds in the UK) you can download it now via the steam client. I bought it together with World in Conflict, which I preferred (partly because I like more conventional war games as opposed to the more Sci Fi orientated), so this game was only aired several times, but I guarantee you won't be disappointed with it. If you have Vista and a DX10 ready video card, this is one of those rare games that's been built around the latest incarnation of direct X, though you don't require DX10 to play it. Watch the Steam video, it's the one that persuaded me to actually buy this last year. I think the game was originally released late in 2007, or early 2008.
http://www.youtube.com/watch?v=5QEet5UNWC4
http://www.youtube.com/watch?v=NKWveMj21mE
http://www.youtube.com/watch?v=DwUjt9Q-ajw